From patchwork Tue Mar 1 06:21:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Zhang, Tianfei" X-Patchwork-Id: 12764194 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98B18C433EF for ; Tue, 1 Mar 2022 06:28:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232628AbiCAGZ4 (ORCPT ); Tue, 1 Mar 2022 01:25:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232585AbiCAGZr (ORCPT ); Tue, 1 Mar 2022 01:25:47 -0500 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8E20B76E27; Mon, 28 Feb 2022 22:24:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646115895; x=1677651895; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=5R3EskLi5TaBVZdnQEcrYdrqfXC1QZeIvpwUfEsGKl0=; b=VifAcRl4DNOETVugxUOZeIr24EMDke/yRv4ZXb37AvKlZgdf6zP7wiLe papDnEnVA2njM5peDR2Ls2+13/CnvBMuNtXjG7pwwcEN5n+0Em7+BjUE5 NZb5Fi+eYAsfABoHjvbBbok4KeHyqSkwahVySQpezHkINZUi4R6mLjqE2 9P3jrmp/mZuPWIa0F9CtEnNn0N6VpYrgP1RY7fhhERgJEe1LQQyvwxv62 VvX7IWNIMwwqLxoJAdedIwuN17nb7dPIyGIHxz0TaqIeZdnWFCMRxAgxW bzs9fBI86lywFGn9j2oTl+tCjbfTE9B5fE8X6xIp5leWb9dXak95ZsmtX w==; X-IronPort-AV: E=McAfee;i="6200,9189,10272"; a="251900336" X-IronPort-AV: E=Sophos;i="5.90,145,1643702400"; d="scan'208";a="251900336" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Feb 2022 22:24:50 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,145,1643702400"; d="scan'208";a="708941808" Received: from unknown (HELO localhost.localdomain.sh.intel.com) ([10.238.175.107]) by orsmga005.jf.intel.com with ESMTP; 28 Feb 2022 22:24:48 -0800 From: Tianfei zhang To: hao.wu@intel.com, trix@redhat.com, mdf@kernel.org, yilun.xu@intel.com, linux-fpga@vger.kernel.org, linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org, corbet@lwn.net, Tianfei zhang Subject: [PATCH v3 5/5] Documentation: fpga: dfl: add description of OFS Date: Tue, 1 Mar 2022 01:21:23 -0500 Message-Id: <20220301062123.818687-6-tianfei.zhang@intel.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20220301062123.818687-1-tianfei.zhang@intel.com> References: <20220301062123.818687-1-tianfei.zhang@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fpga@vger.kernel.org This patch adds description about OFS support for DFL. --- v3: change IOFS to OFS in documentation. v2: * Fixs some typos. * Adds more detail description about the models of AFU access which supported in OFS. Signed-off-by: Tianfei zhang --- Documentation/fpga/dfl.rst | 113 +++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst index ef9eec71f6f3..753507e7b162 100644 --- a/Documentation/fpga/dfl.rst +++ b/Documentation/fpga/dfl.rst @@ -556,6 +556,119 @@ new DFL feature via UIO direct access, its feature id should be added to the driver's id_table. +Open FPGA stack +===================== + +Open FPGA stack aka OFS, a collection of RTL and open software providing interface +to access the instantiated RTL easily in FPGA. OFS leverages the DFL for the +implementation of the FPGA RTL design. + +OFS designs allow for the arrangement of software interfaces across multiple +PCIe endpoints. Some of these interfaces may be PFs defined in the static region +that connect to interfaces in an IP that is loaded via Partial Reconfiguration (PR). +And some of these interfaces may be VFs defined in the PR region that can be +reconfigured by the end-user. Furthermore, these PFs/VFs may also be arranged +using a DFL such that features may be discovered and accessed in user space +(with the aid of a generic kernel driver like vfio-pci). The diagram below depicts +an example design with two PFs and two VFs. In this example, it will export the +management functions via PF0, PF1 will bind with virtio-net driver presenting itself +as a network interface to the OS. The other functions, VF0 and VF1, leverage VFIO +to export the MMIO space to an application or assign to a VM. +:: + + +-----------------+ +--------------+ +-------------+ +------------+ + | FPGA Management | | VirtIO | | User App | | Virtual | + | App | | App | | | | Machine | + +--------+--------+ +------+-------+ +------+------+ +-----+------+ + | | | | + +--------+--------+ +------+-------+ +------+------+ | + | DFL Driver | |VirtIO driver | | VFIO | | + +--------+--------+--+------+-------+ +------+------+ | + | | | | + | | | | + +--------+--------+ +------+-------+ +------+------+ +----+------+ + | PF0 | | PF1 | | PF0_VF0 | | PF0_VF1 | + +-----------------+ +--------------+ +-------------+ +-----------+ + +As accelerators are specialized hardware, they are typically limited in the +number installed in a given system. Many use cases require them to be shared +across multiple software contexts or threads of software execution, either +through partitioning of individual dedicated resources, or virtualization of +shared resources. On OFS, it provides several models to share the AFU +resources via PR mechanism and hardware-based virtualization schemes. + +1. Legacy model. + In legacy FPGA card platforms (like Intel PAC N3000 or N5000 Card),there is + a notion that the boundary between the AFU and the shell is also the unit of + PR for those FPGA platforms. In this model, it can only able to handle a + single context, because it only has one PR engine, and one PR region which + has an associated Port device. +2. Multiple VFs per PR slot. + In this model, available AFU resources may allow instantiation of many of VFs + which has a dedicated PCIe function with their own dedicated MMIO space, or + partition a region of MMIO space on a single PCIe function. + In this model, the Port device would not connected to AFU/PR slot, so we don't + need to release the Port device before creating the VFs. For DFL's view, the AFU + will not connect to Port device, so the Next_AFU pointer in FIU feature header + of port device points to NULL in this model. On the other hand, each VF can start + with an AFU feature header without connected to a FIU Port feature header. +3. Micro-Personas in AFU. + OFS introducing a new concept to extend the FPGA usage, Micro-Personas in + AFU. It finds some downsides of the legacy model to be unacceptable, because + this may be desirable by a customer who intends to switch out one accelerator + for another accelerator without having to reconfigure the entire FPGA. + Micro-Personas allow the developer to designate their own AFU-defined PR + regions. In this model the unit of PR is not the entire AFU, instead + the unit of PR can be any size block or blocks inside the AFU. + In this model, it has PR capability includes one PR engine and multiple PR regions, + and each PR region has an associated port gasket. A PR region may also be + referred to as a PR slot. Port gasket is similar with port device in legacy + model which include the port control, port user clock control and port errors. + +OFS provides the diversity for access the AFU resource to RTL developer. +An IP designer may choose to add more than one PF for interfacing with IP +on the FPGA and choose different model to access the AFU resource. + +There is one reference architecture design using the "Multiple VFs per PR slot" +model for OFS as illustrated below. In this reference design, it exports the +FPGA management functions via PF0. PF1 will bind with virtio-net driver +presenting itself as a network interface to the OS. PF2 will bound to the +vfio-pci driver allowing the user space software to discover and interface +with the specific workload like diagnostic test. To access the AFU resource, +it uses SR-IOV to partition workload interfaces across various VFs. +:: + + +----------------------+ + | PF/VF mux/demux | + +--+--+-----+------+-+-+ + | | | | | + +------------------------+ | | | | + PF0 | +---------+ +-+ | | + +---+---+ | +---+----+ | | + | DFH | | | DFH | | | + +-------+ +-----+----+ +--------+ | | + | FME | | VirtIO | | Test | | | + +---+---+ +----------+ +--------+ | | + | PF1 PF2 | | + | | | + | +----------+ | + | | ++ + | | | + | | PF0_VF0 | PF0_VF1 + | +-----------------+-----------+------------+ + | | +-----+-----------+--------+ | + | | | | | | | + | | +------+ | +--+ -+ +--+---+ | | + | | | Port | | | DFH | | DFH | | | + +-----------+ +------+ | +-----+ +------+ | | + | | | DEV | | DEV | | | + | | +-----+ +------+ | | + | | PR Slot | | + | +--------------------------+ | + | Port Gasket | + +------------------------------------------+ + + Open discussion =============== FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration